Hello and thanks for the post! You should be make to make all of the changes from your .com account. Are you the primary user on your account? When you log in, is your phone number and rate plan listed on the first page towards the middle? If your account is empty when you log in, you more than likely need to register your account information.
All adjustments would be made from your Preferences area.
I keep an eye out for your response!
Sprint Social Care Team